Wednesday, September 26, 2007

Quantum States and Halacha

According to quantum mechanics, nothing at the subatomic scale can really be said to exist until it is observed. Until then, particles occupy nebulous "superposition" states, in which they can have simultaneous "up" and "down" spins, or appear to be in different places at the same time.

Observation appears to "nail down" a particular state of reality, in the same way as a spinning coin can only be said to be in a "heads" or "tails" state once it is caught.

According to quantum mechanics, unobserved particles are described by "wave functions" representing a set of multiple "probable" states. When an observer makes a measurement, the particle then settles down into one of these multiple options.

Quantum mechanics is the science of the smallest components and forces in the physical universe. This is the level where things like light and subatomic particles, the smallest pieces that make up physical substances, are studied and, to some exent, understood (or at least observed, they may not know all the 'how it works', but they do know 'it works like that' by watching it).

In halacha, Jewish law, we hold by the pasuk "the heavens are Hashem's, but the earth is for the children of man", interpreting this to mean that halachic decisions are made here on earth (by appropriately qualified rabbaim). Even if a heavenly voice rings out "it's that way", the ruling of the earthly court holds.

In the time of the Sanhedrin, the great court, Rosh Chodesh, the beginning of the new month, was declared by observation, meaning witness testimony. But, how can observation by people actually change the world, setting the day of the new month?

While I don't have a spiritual answer, I can say that in the science of today, observation by an earthly source has been shown to directly change the physical!